Publication Details
Abstract
The current paper examines the petrophysical characteristics and reservoir potential of the Lower Jurassic Alan, Mus, and Adaiyah formations in two wells in the Kurdistan Region, northeast of Iraq. The conventional wireline logs (gamma ray, density, neutron, and sonic) were processed with the Techlog software to determine shale volume and porosity. Findings indicate that there is a high stratigraphic control over shale and porosity distribution. The most argillaceous unit is the Alan Formation, whose shale content is over 15 percent, and the porosity is negligible (less than 0.5 %), which means that the reservoir quality is poor. Mus Formation has the least shale content (2-6%) and the highest effective porosity (up to 6%), which makes it the target interval. The Adaiyah Formation exhibits intermediate characteristics, and the top layers (AD1 to AD3) are characterized by enhanced porosity (3 to 6%) and decreased shale content. The observations of the inverse relationship between effective porosity and shale volume in both wells can be discussed in terms of regional and international investigations of the Jurassic carbonate reservoirs in the Arabian and Tethyan basins. These results establish a positive correlation between the quality of the reservoir of the Lower Jurassic carbonates and the content of the shale and overprinting by diagenesis. The work offers a new perspective on the heterogeneity and reservoir performance of the Lower Jurassic carbonates in northern Iraq and is part of the overall knowledge of the petroleum system of the Jurassic in the Zagros foreland basin.